LOL, you mean to tell me the boat is doing special "accommodation" for divers who don't carry enough gas to complete a dive safely?
Seriously though, that would be a problem. You might be able to throw the tank that supplies the emergency gas on the line/buoy as well, but now we are getting into a pretty complicated situation NOT recreational.
Hanging gas from divers to do safety stops or extended (unanticipated) deco is fairly common on many charters once the depths are potentially >100ft. Like the Oriskany, NC, and many Great Lakes sites. Actually needing/using that gas is discouraged and you might not be allowed to do dive 2 or get invited back aboard again if you dip into the safety gas - depending on the reason. But its there because a drowning is worse, not just for the diver, for the whole boat.